This paper presents an inverse scattering problem for recovering the shape of multiple conducting cylinders with the immersed targets in a half space by asynchronous particle swarm optimization.Two separate perfect-conducting cylinders of unknown shapes are buried in one half-space and illuminated by the transverse magnetic(TM)plane wave from the other half space.Based on the boundary condition and the measured scattered field,a set of nonlinear integral equation is derived and the imaging problem is reformulated into optimization problem.The asynchronous particle swarm optimization algorithm is employed to find out the global extreme solution of the object function.Numerical results demonstrate even when the initial guesses are far away from the exact shapes,and the multiple scattered fields between two conductors are serious,good reconstruction can be obtained.